So I'm as big a light geek as the rest of you, but I'm not understanding the fascination with square threads on our lights.

Back in high school/trade school I took "machine shop" half a day for 3 years. There was a pretty fair amount of machine tool theory and practice.

Square threads were only used when the screw would be used under greater than normal loads, placing the thread lands more vertical, closer to 90° toward the load, and thickening the root of the thread, not for higher precision or tighter fit.

Perhaps for the illusion of strength. Better made means often more smooth and satisfying. Less chance for crossthreading. And Althrough we do not plan to go to the next vietnam war with out flashlights some of us are particularly attracted to stainless stell flashlights.

-Heavy-No more (and depending on grade, less) resistant to the elements than Aluminum-Terrible Heat Transfer Properties-Nearly impossible to color/coat for protection or cosmetic purposes-Expensive

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I am currently extremely busy with work. Please do not expect a response from me quickly. I will be dropping in as time permits, but the amount of time I can dedicate to responding to topics and PMs is very limited.

Square threading is supposed to be stronger but harder to make. Must be more "valuable" than standard threads. Interms of use, square threads need to be made properly to function well. The square threads on the quarks are quite rough!, while the square threads on the M60R are Super smooth for its size, and have such a nice feel. End of the day, its the quality that matters, not really what threads are used in torches.

Not everyone has 10 flashlights. Having 10 or more flashlights puts less pressure(screw-unscrew cycles) on just one. Somehow it makes sense having square threads if you own one or two flashlights, but not necessarily.If someone buys flashlights just for the fact that he wants to have a SST-50 led, I understand that square threads might mean nothing to him, since the flashlight would be shelf queen.

Flashlights are also built for the military, special law enforcements, so sometimes you really can't pay attention on stuff but they should work easy and have a bit of strength when bashed.

For the regular collector/have many flashlights -use only two, with time it all starts to come down to only how much output the flashlights has, so the square threads become less than secondary in importance, that's the way things are.

From what I've experienced, square threads do have a less chance of crossthreading. My DRY came with some bashed threads where the bezel screws in place. It's not a big deal, since I don't need or have to unscrew that ever. But the tailcap threads could be easily damaged, they are sharp and can easily get blunt and mess the way it screws. It actually doesn't screw from the "first". Everything's better on my Shadow TC6 which has square threads, no worries here.

I like square threads, especially bigger ones (my AKOray K-106 and Sunwayman V10A have big square threads). I think it has more to do with cross-threading and toughness. The really fine threads are easier to ding up, especially the first thread which is critical. If you drop the body tube of a light and it hits on puny threads, it could be game over. That said, I have a structural steel bolt sitting on my desk and it has (big) triangular threads. So if you can use triangular threads for holding steel framed buildings together, then you should be able to use them for flashlights.

You are 100% correct, they are not needed. That being said, they are nicer and given the choice I would prefer them from both a durability (aluminum is malleable and sharp threads deform easier) and an aesthetic point of view.

Aluminum is a very soft metal so square threads are a good idea if you plan on taking the light apart many times. I have seen pictures of people stripping the threads on the end of there light from the wear caused by removing it to replace batteries. Every time you remove the tail cap a small amount of aluminum wears off it can be seen it is the black dust or gunk that turns your clear grease on the threads black. Even though this wear my be microscopic over time eventually the threads will wear completely off, square threading puts more meat directly on these wear points allowing for a longer service life. Anodizing the threads also increase the life of the threads by preventing this wear. The anodized surface is much harder than the bare aluminum and you may notice you do not see the black dust or gunk on anodized threads that means that microscopic wear is minimized.